1. To provide more reliability than a single parity bit can give, an error detecting code scheme uses one parity bit for checking all the odd numbered bits and a second parity bit for all the even numbered bits. What is the:

(a) [4 points] minimum distance?

(b) [4 points] burst-detecting capability?

2. [8 points] Does the TCP protocol impose a limit on the number of clients and servers running simultaneously on a single host? Justify your answer.

3. TCP uses the "slow start" and "additive increase/multiplicative decrease" algorithms to modify the congestion window.

(a) [4 points] What is the initial value of a congestion window?

(b) [4 points] What, if any, is the maximum value of a congestion window?

(c) [10 points] Is there a separate congestion window for each connection that a given host maintains, or do all connections share one congestion window? Write no more than two sentences to justify your answer.

4. A client is transfering a 1Mbyte file to a server using TCP and the socket interface. The client and server are connected to the same network with an MTU (maximum transfer unit) of 1500 bytes. The only traffic on the network is that generated by the file transfer.

(a) [8 points] Could the client use a single write call to transfer the file over the network? (Assume that the integer length passed to and returned by write is represented by a 32 bit number.) Justify your answer.

 (b) [8 points] You attach a monitor to the network to observe the frames that "fly across" the network. The first, third, fifth, seventh, ... frames observed contain segments whose size is 1460 bytes. Allother frames contain segments whose size is 588 bytes. What size TCP receive buffer, in bytes, has the server dedicated to the connection? Justify your answer.

5. Each TCP connection is uniquely identified by an n-tuple.

(a) [0 points] What is n?

(b) [5 points] What n pieces of information comprise the n-tuple?

6. [10 points] Briefly enumerate the differences between the "go back n" protocol defined in Bertsekas and Gallager chapter 2.4.2 and the rules that TCP uses with its sliding window mechanism.

7. [12 points] Draw a diagram of the 7 layer ISO OSI reference model. How do TCP, IP, and ARP fit the model? In your answer, show which of the 7 layers correspond to each protocol, if possible. If the protocols do not fit, explain why.

8. [15points] The client and server code that we went over in class, shown on the reverse side of this sheet, uses the TCP protocol. Suppose we replace the use of the TCP protocol in the code by another transport protocol that provides connectionless datagram service. Would the code still run? Would someone running the program be able to tell that we changed the protocol? If the answer is "yes," then enumerate, using English, what must be changed so that an individual who runs the program cannot tell that you replaced TCP by a connectionless datagram transport protocol. (Hint: What does TCP do that IP does not do? Do any of the socket calls map to TCP concepts, but not to IP concepts?)